Predicting the activation of submicrometer particles into cloud droplets in the atmosphere remains a challenge. The importance of surface tension, σ (mN m–1), in these processes has been evidenced by ...several works, but information on the “surfactants” lowering σ in actual atmospheric particles remains scarce. In this work, PM1 aerosols from urban, coastal, and remote regions of Europe (Lyon, France, Rogoznica, Croatia, and Pallas, Finland, respectively) were investigated and found to contain amphiphilic surfactants in concentrations up to 2.8 μg m–3 in the air and 1.3 M in the particle dry volume. In Pallas, correlations with the PM1 chemical composition showed that amphiphilic surfactants were present in the entire range of particle sizes, supporting recent works. This implied that they were present in hundreds to thousands of particles cm–3 and not only in a few large particles, as it has been hypothesized. Their adsorption isotherms and critical micelle concentration (CMC) were also determined. The low CMC obtained (3 × 10–5–9 × 10–3 M) implies that surface tension depression should be significant for all the particles containing these compounds, even at activation (growth factor ∼ 10). Amphiphilic surfactants are thus likely to enhance the CCN ability of submicrometer atmospheric particles.
Characterizing the size distribution of airborne particles carrying SARS-CoV-2 virus is essential for understanding and predicting airborne transmission and spreading of COVID-19 disease in hospitals ...as well as public and home indoor settings. Nonetheless, few data are currently available on virus-laden particle size distribution. Thus, the aim of this study is reporting the total concentrations and size distributions of SARS-CoV-2- genetic material in airborne particles sampled in hospital and home environments. A nanoMOUDI R122 cascade impactor (TSI, USA) was used to collect size-segregated aerosol down to the sub-micron range in home and in three different hospital environments in presence of infected patients in order to provide the concentration of airborne SARS-CoV-2 genetic material for each particle size range at different sampling locations. Providing one of the largest datasets of detailed size-fractionated airborne SARS-CoV-2 RNA to date, we found that 45.2 % of the total sub- and super-micrometric fractions were positive for SARS-CoV-2 with its genetic material being present in 17.7 % of sub-micrometric (0.18–1 μm) and 81.9 % of super-micrometric (>1 μm) fractions. The highest concentration of SARS-CoV-2 genetic material in total suspended particles (5.6 ± 3.4 RNA copies m−3) was detected in the room occupied with patients with more severe COVID-19 symptoms collected during the patients' high flow nasal oxygen therapy. The highest concentration at certain particle size fraction strongly depends on the sampling environment. However, the contribution of SARS-CoV-2 genetic material was in favour of super-micrometric compared to sub-micrometric particle size range. The evaluation of the individual risk of infection was carried out on the basis of the obtained data considering a hypothetical exposure scenario. The obtained results indicate the necessity of the protective masks in presence of infected subjects, especially while staying for longer period of time in the hospital environments.
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•Airborne SARS-CoV-2 RNA was detected in the hospital and home care environments.•Fine resolution of airborne SARS-CoV-2 RNA size-distribution was reported.•SARS-CoV-2 was detected in 45.2 % of the total sub- and super-micrometric fractions.•SARS-CoV-2 was detected in 17.7 % of sub-micrometric (0.18–1 μm) fractions.•Evaluation of the risk of infection was carried out on basis of the measured data.
Fine particulate matter (PM
2.5
) concentrations at the Middle Adriatic coastal site of Croatia were affected by different air-mass inflows and/or local sources and meteorological conditions, and ...peaked in summer. More polluted continental air-mass inflows mostly affected the area in the winter period, while southern marine pathways had higher impact in spring and summer. Chemical characterization of the water-soluble inorganic and organic ionic constituents is discussed with respect to seasonal trends, possible sources, and air-mass inputs. The largest contributors to the PM
2.5
mass were sea salts modified by the presence of secondary sulfate-rich aerosols indicated also by principal component analysis. SO
4
2−
was the prevailing anion, while the anthropogenic SO
4
2−
(anth-nssSO
4
2−
) dominantly constituted the major non-sea-salt SO
4
2−
(nssSO
4
2−
) fraction. Being influenced by the marine origin, its biogenic fraction (bio-nssSO
4
2−
) increased particularly in the spring. During the investigated period, aerosols were generally acidic. High Cl
−
deficit was observed at Middle Adriatic location for which the acid displacement is primarily responsible. With nssSO
4
2−
being dominant in Cl
−
depletion, sulfur-containing species from anthropogenic pollution emissions may have profound impact on atmospheric composition through altering chlorine chemistry in this region. However, when accounting for the neutralization of H
2
SO
4
by NH
3
, the potential of HNO
3
and organic acids to considerably influence Cl
−
depletion is shown to increase. Intensive open-fire events substantially increased the PM
2.5
concentrations and changed the water-soluble ion composition and aerosol acidity in summer of 2015. To our knowledge, this work presents the first time-resolved data evaluating the seasonal composition of water-soluble ions and their possible sources in PM
2.5
at the Middle Adriatic area. This study contributes towards a better understanding of atmospheric composition in the coastal Adriatic area and serves as a basis for the comparison with future studies related to the air quality at the coastal Adriatic and/or Mediterranean regions.
The traditional voltammetric method at the mercury electrode, and an acidification step developed for the determination of reduced sulfur species (RSS) in natural waters, was for the first time used ...for the quantification of RSS in the water-soluble fraction of fine marine aerosols collected at the Middle Adriatic location (Rogoznica Lake). The evidence of two types of non-volatile RSS that have different interaction with the Hg electrode was confirmed: mercapto-type which complexes Hg as RS–Hg and sulfide/S0-like compounds which deposits HgS. The analytical protocol that was used for RSS determination in aerosol samples is based on separate voltammetric studies of a methyl 3-mercaptopropionate (3-MPA) as a representative of mercapto-type compounds and sulfide as a representative of inorganic RSS. Our preliminary study indicates the presence of mainly RS–Hg compounds in spring samples, ranging from 2.60–15.40 ng m−3, while both, the mercapto-type (0.48–2.23 ng m−3) and sulfide and/or S0-like compounds (0.02–0.26 ng m−3) were detected in early autumn samples. More expressed and defined RS–Hg peaks recorded in the spring potentially indicate their association with biological activity in the area. Those samples were also characterized by a higher water-soluble organic carbon content and a more abundant surface-active fraction, pointing to enhanced solubility and stabilization of RSS in the aqueous atmospheric phase.
Human-induced climate change is expected to increase the frequency and severity of vegetation fires. The Mediterranean region is considered particularly prone to fire episodes in summer. It is well ...known that pyrogenic particles are an important source of external nutrients for the marine environment, especially in oligotrophic areas. In this study, the plankton components of the sea surface layers were integrated to evaluate, for the first time, their dynamics over six months and their response to fire events in a typical coastal area of the Adriatic Sea. Concentrations of nutrients and organic compounds, together with plankton communities were significantly higher in the sea surface microlayer (SML, < 1 mm thick), than in the underlying water from 1 m depth. The piconeuston community and chlorophyll a responded with extreme abundance and concentration to the most intense fire event that enriched the SML with NH4+. Phytoneuston abundance increased with a delay of 2 weeks, while diversity indices decreased slightly after the fire events. The large abundances of the studied piconeuston parameters could be explained by the high availability of organic compounds and the immediate availability of NH4+, while the phytoneuston community responded to an increased NO3‐ concentration, triggered by the fire events. We confirmed that fast-acting marine heterotrophs are important members of biogeochemical cycles associated with fire events and that, together with phytoplankton, they are unavoidable parameters to detect environmental changes.
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•Climate change is expected to increase frequency and severity of vegetation fires•Adriatic coastline is particularly vulnerable to fires in summer•Piconeuston and chlorophyll a responded immediately to NH4+ derived from fire event•Phytoneuston responded to fire events with a delay of 2 weeks
To investigate the temporal variation of aerosol optical properties and evaluate the main emission sources of black carbon (BC) considering different seasons in a typical Mediterranean coastal ...environment, a field campaign was conducted during February–July 2019 at the Central Adriatic coastal area. Real-time measurements of aerosol light absorption were continuously obtained using an aethalometer while the Aethalometer model source apportionment data, optimized by using levoglucosan measurements, were evaluated against the modelling results of the LOTOS-EUROS chemical transport model. The measured mean equivalent BC mass concentration of 0.57 ± 0.64 μg m−3 was the lowest observed in the Mediterranean region. BC from fossil fuel (BCff) dominated the area throughout the study period with a maximum in winter and elevated levels by the approaching summer tourist season. Diel variability of BC concentrations from biomass burning (BCbb) was observed during stable winter conditions, with clear morning and evening concentration peaks, consistent with the profile of residential heating by wood burning. Up to 88% of BC concentrations were attributed to European emission sectors, with stationary source combustion, transportation, shipping and agriculture sectors being the most influential contributors. Source apportionment of BC highlighted that, in addition to biomass burning, small combustion fossil fuel sources, including land traffic and shipping, should be more strictly controlled in order to limit BC pollution in Mediterranean coastal areas. This study serves as a basis of comparison for future studies addressing air quality and pollution source apportionment in the Adriatic and/or the Mediterranean coastal regions in efforts of mitigation and adaptation to climate change.
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•First data on black carbon (BC) concentrations over the coastal zone of the Central Adriatic Sea.•BC sources were apportioned by Aethalometer and LOTOS-EUROS models.•BC from fossil fuel (BCff) dominated the area throughout the study period.•Up to 88% of BC concentrations from European emissions from stationary combustion, transport, shipping and agriculture.•LOTOS-EUROS results were compatible with those of the Aethaletometer model.
Surfactants, or surface-active substances (SAS), are amphipathic organic substances that adsorb on aquatic phase boundaries, including the air-sea interface that covers ~70% of Earth's surface. SAS ...thus mediate all mass transfer across the air-sea interface and are central to planetary scale biogeochemical processes. SAS are routinely quantified in seawater and freshwater in terms of total surfactant activity (SA), using alternating current (AC) out-of-phase voltammetry with a hanging mercury drop electrode (HMDE). Although this technique is well established, method modifications have been implemented and differing calibration procedures adopted in individual research laboratories. Increasing interest in the environmental roles of SAS prompts a timely inter-comparison of these varying analytical approaches. Using sea-surface microlayer (SML: uppermost 80 μm layer sampled) and sub-surface (SSW: 1 m depth sampled) seawater from Jade Bay (south-eastern North Sea), we carried out the first inter-laboratory comparison for SA, using methods and calibration protocols previously established in three participating laboratories. The internal calibration protocol follows direct calibrations of individual samples against the model surfactant Triton-X-100 during analysis, whereas external calibration produces independent Triton-X-100 calibration curves; both protocols express SAS concentrations in Triton-X-100 equivalents (T-X-100 eq.). There was no significant difference between SA derived via internal or external calibration protocols, or by using different analytical instruments (range in Kruskall-Wallis and Dunn-Bonferroni post-hoc test p-values: 0.062–1.000), except where freeze/thaw degradation was suspected to have occurred during transit (p < .001). We recommend using discrete calibration standards during external calibration. Irrespective of any differences in SA determined by the three laboratories, the SA enrichment factor (EF: =SASML/SASSW) was not affected for any sample; the root mean square error (±one standard deviation) between all laboratories was 0.156 ± 0. 226 (n = 45). We present and discuss recommendations for a standard analytical protocol to ensure the inter-laboratory compatibility of SAS measurements into the future.
•An inter-laboratory quantification of total surfactant activity (SA) in seawater•Different calibration protocols produced comparable SA measurements.•Discrete calibration standards must be used during external calibration method.•All tested procedures resulted in comparable SA enrichment factors.
•Improved protocol for the separation of glycolipids: SQDG, MGDG and DGDG.•Marine glycolipids are successfully separated and quantified by the new protocol.•New approach extends the power of TLC–FID ...enabling analysis of 18 lipid classes.
We demonstrate improved power of Iatroscan thin layer chromatography/flame ionization detection (TLC–FID) technique for analysis of complex marine lipid mixture by developing protocol for the separation and analysis of glycolipids including sulfoquinovosyldiacylglycerols (SQDG), monogalactosyldiacylglycerols (MGDG) and digalactosyldiacylglycerols (DGDG). We have modified the common protocol used so far for the analysis of lipid classes by replacing the elution step which uses pure acetone for the elution of acetone mobile polar lipids, with the elution step containing chloroform–acetone (72:28, v:v) for separation of MGDG and DGDG. To separate SQDG from the complex lipid matrix we introduced solvent mixture acetone–chloroform–methanol–formic acid (33:33:33:0.6, v:v:v:v). Quantification of glycolipid classes was performed after calibration with glycolipid standards for the masses between 0.2 and 2.7–5.0μg. With this new protocol we have successfully separated three glycolipids from the complex particulate lipid mixture of the seawater samples. Such an approach extends the power of existing protocol for the analysis of lipids which altogether ensure detection and quantification of 18 lipid classes what was demonstrated on seawater samples. This enables to gain a very broad system overview of the particularly complex environments as are seas, oceans and freshwaters.
Abstract
The assimilation of inorganic nutrients by phytoplankton strongly depends on environmental conditions such as the availability of nitrogen and temperature, especially warming. The ...acclimation or adaptation of different species to such changes remains poorly understood. Here, we used a multimethod approach to study the viability and physiological and biochemical responses of the marine diatom Chaetoceros pseudocurvisetus to different temperatures (15, 25, and 30 °C) and different N:P ratios. Nitrogen limitation had a greater effect than high temperature on cell growth and reproduction, leading to a marked elongation of setae, decreased phosphorus assimilation, increased lipid accumulation, and decreased protein synthesis. The elongation of setae observed under these conditions may serve to increase the surface area available for the uptake of inorganic and/or organic nitrogen. In contrast, high temperatures (30 °C) had a stronger effect than nitrogen deficiency on cell death, nitrogen assimilation, chlorophyll a accumulation, the cessation of setae formation, and cell lipid remodelling. Significant changes in thylakoid lipids were observed in cells maintained at 30 °C, with increased levels of digalactosyldiacylglycerol and sulfoquinovosyldiacylglycerol. These changes may be explained by the role of galactolipids in thylakoid membrane stabilization during heat stress.
Atmospheric deposition (AD) of nutrients and its impact on the sea surface requires consideration of interfacial processes within the sea surface microlayer (SML), the ocean-atmosphere boundary layer ...of major importance for many global biogeochemical and climate-related processes. This study comprised a comprehensive dataset, including dissolved NO3−, NH4+ and PO43− in ambient aerosol particles, wet deposition and sea surface samples collected from February to July 2019 at a central Adriatic coastal site. The aerosol mean concentration of dissolved nitrogen (DIN = NO3− + NH4+) and PO43− were 48.8 ± 82.8 μmol m−3 and 0.8 ± 0.6 μmol m−3, respectively, while their total fluxes (dry + wet) ranged from 24.2 to 212.3 μmol m−2 d−1 (mean 123.2 ± 53.2 μmol m−2 d−1) and from 1.2 to 2.1 μmol m−2 d−1 (mean 1.5 ± 0.3 μmol m−2 d−1), respectively. Intensive local episodes of open biomass burning (BB) significantly increased aerosol DIN concentrations as well as DIN deposition fluxes, particularly altering the molar DIN/PO43− ratio of atmospheric samples. The DIN temporal patterns showed high variability in the SML (range 0.2–24.6 μmol L−1, mean 5.0 ± 7.1 μmol L−1) in contrast to the underlying water samples (range 0.5–4.2 μmol L−1, mean 1.9 ± 1.2 μmol L−1), with significant increases during BB periods. Variability in abundance of heterotrophic bacteria and autotrophs in the SML along with concentrations of bulk dissolved and particulate organic carbon as well as dissolved and particulate lipids and carbohydrates, gel particles and surfactants followed DIN enhancements with a two-week delay. This study showed that AD can affect the short-term scale enrichments of organic matter in the SML, especially when accompanied by BB emissions typical of the overall Mediterranean coastal environment. This could have strong implications for global air-sea exchange processes, including those of climate relevant gases, mediated by the SML.
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•Adriatic coastal area: simultaneous atmospheric and seawater field measurements•Nutrient variability in aerosols, rainwater and atmospheric deposition (AD) fluxes•Local open-fire biomass burning (BB) affected chemistry of atmospheric samples.•AD impacted nutrient levels and N:P ratios in the sea surface microlayer (SML).•The SML plankton development and organic matter enrichments followed BB episodes.
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